Elizabeth II (Elizabeth Alexandra Mary; born 21 April 1926) is the constitutional monarch of 16 sovereign states known as the Commonwealth realms, and head of the 54-member Commonwealth of Nations. She is also head of state of the Crown Dependencies.

On her accession in 1952, she became Head of the Commonwealth and queen regnant of seven independent Commonwealth countries: the United Kingdom, Canada, Australia, New Zealand, South Africa, Pakistan, and Ceylon. Between 1956 and 1992, the number of her realms varied as territories gained independence and some realms became republics. Today, in addition to the first four aforementioned countries, Elizabeth is Queen of Jamaica, Barbados, the Bahamas, Grenada, Papua New Guinea, the Solomon Islands, Tuvalu, Saint Lucia, Saint Vincent and the Grenadines, Belize, Antigua and Barbuda, and Saint Kitts and Nevis.

Her reign of 60 years is the second longest for a British monarch; only Queen Victoria has reigned longer. Elizabeth's Diamond Jubilee is being celebrated during 2012.